LLN, le 17/11/06
Dear SPMers,
I'd like to echo the recent posts on using/not_using slice timing
correction with block designs.
(1) I often read/heard people saying that slice timing should not be
done with a block design, but, as I understand, there is not such a
strong rule. I must confess that I don't see exactly why slice timing
would be useless in a block design. If timing interpolation improves
the signal (leaving aside the multiple reslicing issue), it should do
so whatever the design, shouldn't it? After all, the averaging across
volumes is taking place AFTER the timing interpolation... What am I
missing here?
(2) I usually use slice timing with block designs with TR<3sec. As a
wild check, I re-analysed a couple of subjects without slice-timing.
I confirm what Daniel Simmonds mentioned in his post (see
<http://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind0610&L=spm&D=0&O=D&P=5702>):
results are highly similar, but those with the slice timing
correction have generally bigger clusters and t-values (although this
was not true for all the clusters), even for blocks longer (28 sec,
TR=2 sec) than those mentioned in the post.
(3) Is there any clever reply for a referee who's wondering why I
used slice timing with a block design in a manuscript under review???
Thanks for any comment,
Mauro.
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Mauro PESENTI
Research Associate, National Fund for Scientific Research (Belgium)
Unite de Neurosciences Cognitives
Departement de Psychologie
Universite Catholique de Louvain
Place Cardinal Mercier, 10
B-1348 Louvain-la-Neuve
tel.: +32 (0)10 47 88 22
fax: +32 (0)10 47 37 74
E-mail: [log in to unmask]
http://www.nesc.ucl.ac.be
http://www.nesc.ucl.ac.be/mp/pesentiHomepage.htm
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